1. Technical Field
The present invention relates to a light emitting device, a manufacturing apparatus and method thereof, and an image printing apparatus.
2. Related Art
There is an image printing apparatus in which an image carrier such as a photosensitive drum is charged, a latent image is formed on a photosensitive surface thereof, and toner is attached onto the latent image, thereby forming an image to be transferred onto other object. The image printing apparatus includes a light emitting device which irradiates light onto the photosensitive surface to form the latent image. The light emitting device many include a light emitting substrate on which a plurality of light emitting elements are arranged to form an optical image. Further, the light emitting device may include a focusing lens array which forms an image on the photosensitive surface by transmitting light received from the light emitting substrate.
In the focusing lens array, light used to form the optical image is incident from one end thereof and light used to form an erect image of a corresponding optical image is emitted from the other end thereof. If a distance between an optical imaging surface of the light emitting substrate and the focusing lens array is equal to an object distance, and a distance between the focusing lens array and the photosensitive surface is equal to an image surface distance, the light emitting device having the focusing lens array can form an erect image having the same magnification as the optical image formed on the optical imaging surface. Meanwhile, if the distance between the focusing lens array and the photosensitive surface is not equal to the image surface distance, there is deterioration in precision of the image formed on the photosensitive surface, and further printing quality of the image printing apparatus.
The image surface distance is defined as an ideal distance between the other end of the focusing lens array and the photosensitive surface, and is determined by a distance between one end of the focusing lens array and the other end thereof, that is, a thickness of the focusing lens array. Since the thickness of the focusing lens array has a manufacturing variation (for example, ±0.1 mm), the image surface distance also has the manufacturing variation. That is, the image surface distance is intrinsic to the focusing lens array.
By taking the above description into account, a technique has been proposed to adjust the distance between the focusing lens array and the image carrier. An example of the technique may include a technique which adjusts the distance between a lens array and the photosensitive drum by rotating an adjusting screw and has a structure in which, while a holder that supports the lens array is urged towards the photosensitive drum by a leaf spring, the front end of the adjusting screw that passes through a corresponding holder is screw-bonded so as to come in contact with a member that supports the photosensitive drum (see Japanese Patent No. 3,178,623, FIG. 1).
However, in this technique, a mechanical adjusting tool such as the adjusting screw is required, and thus a structure of the light emitting device becomes complex. Further, after the distance between the focusing lens array and the image carrier is determined, if the adjusting screw unexpectedly rotates, the distance deviates from an optimum distance. Furthermore, although a mechanical tool may be installed to avoid this deviation, the structure of the light emitting device may be further complex.